[llvm] [AMDGPU] Convert flat scratch SS->SV in FI elimination (PR #166979)

[Diana Picus via llvm-commits]

================
@@ -0,0 +1,630 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 6
+; REQUIRES: amdgpu-registered-target
+; Ensure we don't crash with: "Cannot scavenge register in FI elimination!"
----------------
rovka wrote:

Nit: It's better to put comments after the RUN lines, otherwise people might miss them.

https://github.com/llvm/llvm-project/pull/166979